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Registered
Join Date: Sep 2003
Location: cali
Posts: 41
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3.2L constant smoke at low speeds
Ok, I have an 88 carrera w/ 105k miles on the original 3.2 litre engine (no rebuild). Recently, I have noticed more and more smoke out the tail (through my sideview mirror) while driving in traffic on the highway (5-20mph in 1st/2nd gear usually low RPM). Obviously, when I speed up it goes away (im assuming because the wind disperses it quicker).
The strange thing, is that when the car is sitting and idling...no visible smoke (or at least much less smoke), even if I race the engine. My initial thoughts....a leak from return tubes, onto heat exchangers? (but u would see that a rest, right?) Any ideas of obvious things to check?,...please dont say rebuild! FYI: I burn about 1quart every 800-1000miles Thnks for your advice. Fucherman
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fucherman |
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09-22-2003, 08:56 AM
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Location: San Francisco Bay Area
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I would have someone check your Air Fuel ratio. If you are running rich at low to partial throttle you would see smoke as you describe (this is assuming you are seeing white smoke). When was the last time your O2 sensor was replaced?
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Bill |
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09-22-2003, 09:11 AM
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Location: cali
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Yes, the o2 sensor was checked recently,.....
Actually, funny you mention 'running rich'. I recently replaced the DME computer (the original was damaged) and quickly noticed a change in performance. The new computer (actually used from another 911) was supposedly 'chipped' and supposed to improve performance....the only thing I notice is a strangely low idle and flat spots in acceleration... do you think the DME and smoke could be the same problem? could replacing the stock chip solve everything? thanks again for any help.
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fucherman |
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09-22-2003, 09:18 AM
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Friend of Warren
Join Date: Oct 2000
Location: Lincoln, NE
Posts: 16,494
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What color is the smoke?
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Kurt V No more Porsches, but a revolving number of motorcycles. |
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09-22-2003, 09:19 AM
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Smoke is mostly white, w/ a slight blue tint...and there is a smell also...very rich smell (I want to say catconverter type smell but I guess could be oil)
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fucherman |
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09-22-2003, 09:21 AM
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Friend of Warren
Join Date: Oct 2000
Location: Lincoln, NE
Posts: 16,494
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Hmmm, too rich fuel mixture = grey or black smoke. White with/blue generally = oil burning. Could be a number of things.
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Kurt V No more Porsches, but a revolving number of motorcycles. |
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09-22-2003, 09:35 AM
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Join Date: May 2003
Location: Nor. Cal.
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I'd get things checked quickly for the potential "running (very) rich" situation. Such a situation can lead to destroying your catalytic converter, and replacing it is not a cost you want to deal with.
Tom
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09-22-2003, 10:05 AM
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Changing the DME can certainly change your mixture - particularly if the new DME box has a performance chip in it as these chips usually play with the AF ratio to get better performance.
As for the color of the smoke - generally running rich under load will get you black smoke (you may have seen this before when another car punches it and leaves a cloud of black smoke it its wake). However, from my expeience, running slightly rich under no or partial load gives you white/grey smoke. At least that is what my 911 did when I was adjusting the AF ratio during the installation and tuning of a Mass Air Flow unit.
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Bill |
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09-22-2003, 10:46 AM
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